1. Field of the Invention
This invention relates to a wireless power transfer system for receiving sunlight, executing photoelectric conversion of the sunlight to generate power, transmitting a microwave generated based on the power from a plurality of transmitters, receiving the microwave by a receiver, and generating power, and a power transmitter and a rectenna base station used in the wireless power transfer system.
2. Description of the Related Art
For example, JP-A-2005-319853 describes a related-art wireless power transfer system for executing power transfer with a microwave from a power generating satellite placed on orbit in space to a ground receiver. In the related-art wireless power transfer system, a pilot signal transmitted from a rectenna base station is received in the power generating satellite and a pilot reply signal is transmitted to the rectenna base station. The pilot signal is subjected to spread spectrum modulation and is identified for each satellite and a reference phase is taken out. On the other hand, the pilot reply signal is also subjected to spread spectrum modulation and in the rectenna base station, the phase information of each pilot reply signal is extracted and the phase delay of each power generating satellite is found and a feedback system of reflecting the phase delay on the phase of the pilot signal is formed, whereby the phases of the microwaves from the power generating satellites are made uniform and larger power is provided.
According to the wireless power transfer system described in JP-A-2005-319853, the ground rectenna base station needs a circuit for executing spread spectrum modulation of the pilot signal to be transmitted and executing inverse spread spectrum demodulation of the received pilot reply signal and a circuit for comparing the phases of the pilot reply signals for each satellite provided by executing the inverse spread spectrum modulation and feeding back to match the phases and involves a problem of an increase in the facilities. Each satellite in orbit also needs a circuit for executing inverse spread spectrum demodulation of the pilot signal and executing spread spectrum modulation of the pilot reply signal for generation and involves a problem of an increase in the circuit scale; in addition, power for driving the circuitry becomes necessary and a part of power generated by photoelectric conversion is consumed by the circuit involved in the pilot signal and the whole power generation efficiency is degraded; this is also a problem.